Polyethyleneimine-oleic acid micelle-stabilized gold nanoparticles for reduction of 4-nitrophenol with enhanced performance

Noble metal nanoparticles have been drawing great attention for the treatment of water pollutants. The catalytic activity of noble metal nanoparticles is usually reduced due to their aggregation. Amphiphilic molecule micelles have potential to stabilize the noble nanoparticles against aggregation. In this study, a novel facile method was reported for preparing polyethyleneimine-oleic acid (PEI-oleic acid) micelle-stabilized gold nanoparticles (PO-AuNPsn), where the gold nanoparticles (AuNPs) were embedded in the shell area of micelles. When the molar ratio of [N] to [Au] was 50, 100, and 200, the mean diameter of AuNPs was 3.52 ± 0.42, 3.11 ± 0.28, and 2.85 ± 0.48 nm, respectively. The corresponding zeta potential of the PO-AuNPsn was determined to be 26.2, 28.9 and 35.7 mV, respectively. Furthermore, PO-AuNPsn remained stable in aqueous solution at room temperature for more than 1 month. More importantly, PO-AuNPsn had higher catalytic activity for 4-nitrophenol (4-NP) reduction in aqueous solution compared with previous reports, where PO-AuNPs200 showed a Knor value of 9367 s−1 g−1. It is believed that PO-AuNPsn showed high catalytic activity because of their small size, high stability, and the location of AuNPs in the shell area, which made it easier for AuNPs to contact with 4-NP. The method described in this report represents a new method to prepare small and stable noble metal nanoparticles for catalytic applications in the future.